1. Field of the Invention
The present invention relates generally to optical systems, and more specifically to an assembly that flexurally suspends a mirror to reflect millimeter wave energy to a radiometer.
2. Description of the Prior Art
Mirrors are often used in imaging systems to direct electromagnetic radiation for various applications such as lasers, x-rays, and thermal imaging. There are static type mirrors that are fixed permanently into position. This type of static system has been used with aircraft performing reconnaissance over a designated area. The mirror on the aircraft is fixed so that the aircraft is required to maneuver to focus the mirror on a larger area to complete a survey. This is a shortcoming in functionality that has been addressed with another type of mirror system that has the ability to be adjusted and rotated about an axis or axes.
Both aircraft and satellite cameras have used flexurally suspended mirrors for decades. They generally move about only one axis.
The scanning mechanism that is the subject of this invention uses a flexurally suspended mirror in a millimeter wave imaging system. A millimeter wave imaging system uses either active or passive detection and measurement of electromagnetic radiation at millimeter wavelengths. The contrast in radiation between the surrounding background environment and individual undergoing a scan identifies concealed objects under clothing.
In an adjustable mirror system, the mirror is used to scan the imaging zone and redirect millimeter wave energy to the focal plane of a lens. This reduces the required size of the radiometer. The mirror is mounted on a universal joint about two perpendicular axes. The universal joint provides the pivot point as actuators position the mirror as desired. However, this type of prior art system is not suited for scanning at a rapid rate. Furthermore, the universal joint is susceptible to failure and vibration as it becomes worn from use.
To overcome the failure of universal joints, the prior art describes an alternative mirror mount whereby a rod and flexible neck serve as a substitute for a universal joint to support the mirror. Actuators are used to tilt the mirror about the flexible neck and a diaphragm secures the mirror to the support body. However, a shortcoming of this type of system is the small field of scanning of less than 1 degree.
Accordingly, there is a need for a mirror scanning system that has the ability to scan a large field of view.
There is also a need in the art for an improved mirror scanning system that is accurate and not susceptible to wear of the assembly after normal operation.
It is, therefore, to the effective resolution of the aforementioned problems and shortcomings of the prior art that the present invention is directed.
However, in view of the prior art at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the identified needs could be fulfilled.